Entry Task

Write down your age

Multiply it by 10

Add 8 to the product

Double that answer and subtract 16

Divide the result by 20

Explain what you notice. Why does it work?

Reasoning in Algebra and Geometry

2.5

Learning Target: I can use algebraic properties in geometry to solve problems and justify my

steps.

I accept postulates and properties to be true

P. 902-910• These pages should be booked marked in

your text. This is where all theorems and postulates are located that you can use while doing proofs.

Proofs -

• When writing a proof, it is important to justify each logical step with a reason. You can use symbols and abbreviations, but they must be clear enough so that anyone who reads your proof will understand them.

Conclusion

• Definitions• Postulates• Properties• Theorems

Hypothesis

If a diagram for a proof is not provided, draw your own and mark the given information on it. But do not mark the information in the Prove statement on it.

Helpful Hint

Proof

Table Groups• Let’s not worry just yet about a “two

column” proof. Let’s see if your group can argue with me and prove this:

Writing a Two-Column Proof

• Write a two-column proof.

Given:

Prove:

1 3m m

m AEC m DEB

Writing a Two-Column Proof

Homework

• Homework– p. 117 #1-13,20• Challenge - #25

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